The overall objective of this project is to study membrane- associated immunological phenomena using lipid model membrane systems. Previous investigations have concentrated on the mechanism by which antibody-complement produces immune damage of liposomes sensitized with naturally occuring lipid antigens (e.g. mammalian ceramides or bacterial lipopolysaccharides). In more recent experiments, these antigens were replaced by synthetic phosphatidylethanolamine (PE) derivatives in which the amino function was substituted with different haptens (e.g. dinitrophenylaminocaproyl or mono(p-azobenzenearsonic acid) tyrosyl). Subsequent studies revealed that liposomes, actively sensitized with the N-substituted PE derivatives, are per se immunogenic as evidenced by induction of either humoral and/or cell-mediated responses. In these liposomes, the haptens are inserted non-covalently within lipid bilayers which serve a carrier role. Current efforts mainly concern various parameters of the immunogenicity of these novel immunogens because they differ significantly from conventional preparations in which determinants are covalently attached to carriers such as proteins. Bibliographic references: Uemura, K., Claflin, J.L., Davie, J.M., and Kinsky, S.C., "Immune Response to Liposomal Model Membranes: Restricted IgM and IgG Anti-dinitrophenyl Antibodies Produced in Guinea Pigs", J. Immunol. 114, 958 (1975); Nicolotti, R.A., and Kinsky, S.C., "Immunogenicity of Liposomal Model Membranes Sensitized with Mono(p- azobenzenearsonic acid) tyrosylphosphatidylethanolamine Derivatives, Antibody Formation and Delayed Hypersensitivity Reaction", Biochemistry 14, 2331 (1975).